黄土岩溶泉岩溶发育特征综合研究

Comprehensive Research on Development Characteristics of Loess Karst Spring

为进一步查明黄土地下水岩溶作用的强弱与变化规律，我们于2004年6月到2005年6月对长安县杨万村黄土岩溶泉进行了每月2次的观测，实验结果显示：杨万村岩溶泉pH值变化在6．89～7．38之间，年均值为7．12，具弱碱性特点；电导率变化在634．36～758．27μs·cm^-1之间，年均值为681．61μs·cm^-1。从当年6月到次年6月，黄土岩溶泉pH值在总体上呈现降低-升高降低的变化规律，电导率呈现降低-升高的变化规律，pH值波动性较大。岩溶泉水的pH值和电导率受降水量、水温和CO2含量高低控制。水温、降水量和CO2含量高的夏、秋季，pH值小、电导率大；水温、降水和CO2含量低的冬、春季，pH值大、电导率小。由岩溶泉水的pH值和电导率大小变化得知，夏、秋季该泉岩溶作用强，冬、春季岩溶作用弱。与镇安渔洞河灰岩岩溶泉相比，黄土岩溶泉流量稳定、pH值低、电导率高，且pH值、电导率日变化显著。存在差异的主要原因为两地岩溶水的补给方式不同，黄土岩溶泉水具有典型地下水的特征，以薄膜水缓慢补给为主，而渔洞河岩溶泉以管道和重力水快速补给为主。

In order to find out the power of karst process and the law of loess karst spring further, we carried on the observation of loess karst spring twice a month in Yangwan Village of Chang＇ an County from June 2004 to June 2005. The result showed that： The change of pH value is between 6.89. and 7.38, the annual average number is 7. 12, which has alkalescency characteristics. The conductivity change of the karst spring is between 634.36 and 758. 27 s·cm^-1, the annual average number is 681.61 s·cm^-1. From June of this year to June next year, the pH value of loess karst spring demonstrated a law of ＂fall to rise then to fall＂ on the whole, but conductivity rate appeared the law of ＂high to low then to high again＂. For details, the pH value fluctuated relatively heavily. The pH value and conductivity of karst spring are controlled by precipitation, temperature and CO2. content. In summer and autumn, when water temperature, precipitation and the content of CO2 are high, the pH value is small and the conductivity is large. In winter and spring, when water temperature, precipitation and the content of CO2 are low, the pH value is large and the conductivity is small. From the change of pH value and conductivity rate, we learned that karst spring process is stronger in summer and autumn but weaker in winter and spring. Compared with limestone karst spring in Yudonghe, the spring water of loess karst spring flows more stably, its pH value is lower and conductivity rate is higher; besides, their daily changes are remarkable. The differentiation of water replenishment can answer for these diversities between loess karst spring and limestone karst spring： loess karst spring mainly supplied by membrane water, limestone karst spring mainly by gravity water and conduit water.